A Comparative Study Of The Same Gemstones Synthesized By Different Methods

With the development of technology,the synthetic methods of gemstones become more and more perfect,and the kinds of synthetic gemstones become more and more.The chemical composition,crystal structure and gemmological properties of gemstones synthesized by different methods are basically the same as those of natural gemstones,therefore,the identification of synthetic gemstones has become one of the most important and difficult problems in gemmology.In this paper,the synthetic diamond,ruby,sapphire,emerald and the corresponding natural gemstones were measured by UV-VIS-NIR Spectra,IR Spectra and Raman Spectra.The Raman characteristic peaks are fitted and the FWHM is analyzed,the analysis shows that:1.There are differences in fluorescence characteristics,UV spectrum characteristics and FWHM between natural diamond and synthetic diamond.The fluorescence of natural diamond in long wave is stronger than that in short wave,and that of synthetic diamond in short wave is stronger than that in long wave;There are415 nm and 478 nm absorption peaks in natural diamonds,but not in synthetic diamonds;The FWHM of natural diamond is higher than that of synthetic diamond;The fluorescence characteristics,UV spectrum characteristics and FWHM of diamond synthesized by different methods are basically the same.2.The conventional gemmological characteristics of natural ruby and synthetic ruby are basically the same,but there are differences in ultraviolet spectrum,infrared spectrum and FWHM.The absorption bandwidth of synthetic ruby is 320nm,but natural ruby has no such characteristic;Some samples synthesized by hydrothermal method have weak absorption bands around 3231cm^-1,3305cm^-1,3478cm^-1 and3562cm^-1;The FWHM of natural ruby is higher than that of synthetic ruby;The UV spectra of ruby synthesized by different methods are different.The ruby synthesized by Czochralski method has no absorption at 478 nm;There is no significant difference in FWHM of ruby synthesized by different methods.3.The conventional gemmological and infrared spectral characteristics of natural sapphire and synthetic sapphire are basically the same,but the ultraviolet spectral characteristics and FWHM are different.Natural sapphire has absorption peaks at 387nm,452 nm and 566 nm,but synthetic sapphire has no obvious absorption peak;The FWHM of natural sapphire is higher than that of synthetic sapphire;There is no significant difference in UV,IR and FWHM of sapphire synthesized by different methods.4.The conventional gemmological and mid infrared spectral characteristics of natural and synthetic emeralds are basically the same,but there are differences in UV,NIR and FWHM.There are wide absorption bands at 450 nm and 620 nm for natural emeralds and synthetic emeralds,while there are absorption peaks at 370 nm,683 nm and 956 nm for hydrothermal emeralds;Both natural emeralds and hydrothermalemeralds have water absorption peaks,while flux synthesized emeralds have no water absorption peaks;The FWHM of natural emerald is higher than that of synthetic emerald;There is no significant difference in FWHM of emeralds synthesized by different methods.